I. Field of the Invention
The present invention relates to wireless telecommunications. More particularly, the present invention relates to a novel and improved method and apparatus for paging a cellular telephone or other wireless communications device.
II. Description of the Related Art
The IS-95 cellular telephone standard (and its derivatives such as IS-95A and ANSI J-STD-008 referred to herein collectively as IS-95) uses advanced signal processing techniques to provide efficient and high quality cellular telephone service. For example, an IS-95 compliant cellular telephone system utilizes vocoding, error detection, forward error correction (FEC), interleaving and spread spectrum modulation in order to make more efficient use of the available RF bandwidth, and to provide more robust connections. In general, the benefits provided by IS-95 include longer talk time, higher capacity, and fewer dropped calls when compared to other types of cellular telephone systems.
To conduct communications in an orderly manner, IS-95 provides a set of highly encoded channels over which data having different functions is transmitted. These highly encoded channels include a paging channel over which paging messages are transmitted notifying cellular telephones or other types of wireless terminals that an incoming request to communicate is pending. In accordance with the IS-95 standard, paging messages are transmitted at low to medium data rates (4800 or 9600 bps) during time slots that are preassigned to groups of cellular telephones. Table I provides the data included in a General Page Message as an example of typical a paging message generated substantially in accordance with the IS-95A standard.
TABLE IMessage FieldLength (Bits)MSG_TYPE (Message Type)8CONFIG_MSG_SEQ6ACC_MSG_SEQ6CLASS_0_DONE1CLASS_1_DONE1RESERVED2BROADCAST_DONE1RESERVED4ADD_LENGTH3ADD_PFIELD8 × ADD_LENGTHAnd zero or more occurrences of the following page record:PAGE_CLASS2PAGE_SUBCLASS2Page class specific fieldsTypically 2-12 bytes.
Table I is provided simply to illustrate the length of a typical paging message, so a detailed description of the function of each field is not included herein. Such a detailed description may obtained, however, by referring to the well known, and publicly available, IS-95 standard (in particular the IS-95A standard). The paging messages also begin with an eight bit message length field (MSG_LEN), that indicates the length of the message, and end with a 30 bit cyclical-redundancy-check (CRC) field (not shown).
To monitor for paging messages, a cellular telephone periodically monitors the paging channel during the assigned paging slot. In particular, the cellular telephone periodically activates complex RF and digital signal processing circuitry for as long as is necessary to successfully process the paging message. Since the typical paging message is relatively long, and transmitted via a highly encoded low to medium rate channel, the associated processing during each paging slot requires a significant amount time and signal processing resources, and therefore requires a significant amount of power to complete. This reduces the amount of time an IS-95 cellular telephone can remain in standby mode using a battery of given capacity, and therefore is highly undesirable.